1. Field of the Invention
The present disclosure relates to techniques for admission control in communication networks. In particular, the disclosure pays specific attention to the possible application to local area networks (LANs) such as, e.g., a wireless LAN.
The disclosure is also adapted for use, e.g., in non-wireless networks (such as the Ethernet), other types of wireless networks (UltraWideBand), or mobile telephone networks including terminals equipped with a WLAN interface.
2. Description of the Related Art
Wireless LANs (WLANs) are becoming increasingly popular not just for data transmission but also for real time streaming applications.
WLANs are being increasingly introduced in domestic environments mainly for sharing access to a broadband Internet connection. IEEE802.11b (see IEEE802.1Ib standard, “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications”, 1999 edition) running at 11 Mbps is widely used nowadays, while higher speed IEEE802.11g at 54 Mbps is being gradually introduced. Consumer electronics manufacturers also are interested in using a domestic WLAN to distribute audiovisual content among entertainment devices and PC's.
However, none of the above-mentioned standards has been developed to support streaming services, which require strict quality of service (QoS) guarantees in terms of delay and delay variation.
The lack of quality of service (QoS) support at the MAC (Medium Access Control) layer of existing WLANs makes audio video streaming particularly sensitive to interfering data traffic.
Streaming media over a Wireless LAN is relatively simple in the ideal case of a channel with a limited error rate and without interference. In practice, however, the attenuation of the signal caused by walls and multipath effects of a closed environment such as a home environment sometimes result in a high (and variable) bit error rate. Furthermore, as wireless equipment in the 2.4 and 5 GHz ISM bands is becoming commonplace, multiple users may be sharing the same radio spectrum in an uncoordinated way, thereby producing mutual interference.
The consequence of transmission errors and interference thus generated is twofold.
Firstly, the need of re-transmitting frames causes bandwidth waste.
Secondly, such retransmissions increase the jitter of frames that arrive at the receiver of a real-time flow: a bigger buffer is therefore needed to compensate for the ensuing delay variations.